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Groeneweg S, Zevenbergen C, Lima de Souza EC, van Geest FS, Kloeckener-Gruissem B, Laczko E, Camargo SMR, Meima ME, Peeters RP, Visser WE. Identification of Iodotyrosines as Novel Substrates for the Thyroid Hormone Transporter MCT8. Thyroid 2024; 34:931-941. [PMID: 38661522 DOI: 10.1089/thy.2023.0551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Background: Monocarboxylate transporter 8 (MCT8) is the most specific thyroid hormone transporter identified to date, deficiency of which has been associated with severe intellectual and motor disability and abnormal serum thyroid function tests. However, it is presently unknown if MCT8, similar to other thyroid hormone transporters, also accepts additional substrates, and if disruption of their transport may contribute to the observed phenotype. Methods: In this study, we aimed to identify such substrates by applying liquid chromatography-mass spectrometry-based metabolome analysis in lysates of control and MCT8-overexpressing Xenopus oocytes. A subset of identified candidate substrates were validated by direct transport studies in transiently transfected COS-1 cells and human fibroblasts, which endogenously express MCT8. Moreover, transport characteristics were determined, including transport saturation and cis-inhibition potency of thyroid hormone transport. Results: Metabolome analysis identified 21 m/z ratios, corresponding to 87 candidate metabolites, with a 2.0-times differential abundance in MCT8-injected oocytes compared with controls. These metabolites included 3,5-diiodotyrosine (DIT) and several amino acids, including glutamate and glutamine. In accordance, MCT8-expressing COS-1 cells had 2.2-times lower intracellular accumulation of [125I]-DIT compared with control cells. This effect was largely blocked in the presence of 3,3',5-triiodothyronine (T3) (IC50: 2.5 ± 1.5 µM) or thyroxine (T4) (IC50: 5.8 ± 1.3 µM). Conversely, increasing concentrations of DIT enhanced the accumulation of T3 and T4. The MCT8-specific inhibitor silychristin increased the intracellular accumulation of DIT in human fibroblasts. COS-1 cells expressing MCT8 also exhibited a 50% reduction in intracellular accumulation of [125I]-3-monoiodotyrosine (MIT). In contrast, COS-1 cells expressing MCT8 did not alter the intracellular accumulation of [3H]-glutamate or [3H]-glutamine. However, studies in human fibroblasts showed a 1.5-1.9 times higher glutamate uptake in control fibroblasts compared with fibroblasts derived from patients with MCT8 deficiency, which was not affected in the presence of silychristin. Conclusions: Taken together, our results suggest that the iodotyrosines DIT and MIT can be exported by MCT8. MIT and DIT interfere with MCT8-mediated transport of thyroid hormone in vitro and vice versa. Future studies should elucidate if MCT8, being highly expressed in thyroidal follicular cells, also transports iodotyrosines in vivo.
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Affiliation(s)
- Stefan Groeneweg
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
- Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Chantal Zevenbergen
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
- Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Elaine C Lima de Souza
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
- Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Ferdy S van Geest
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
- Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Barbara Kloeckener-Gruissem
- Institute of Medical Molecular Genetics, University of Zurich, Schlieren, Switzerland
- Department of Biology, ETHZ, Zurich, Switzerland
| | - Endre Laczko
- Functional Genomics Center, University and ETH Zurich, Zurich, Switzerland
| | - Simone M R Camargo
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Marcel E Meima
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
- Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Robin P Peeters
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
- Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - W Edward Visser
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
- Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
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Braun D, Bohleber S, Vatine GD, Svendsen CN, Schweizer U. Sodium Phenylbutyrate Rescues Thyroid Hormone Transport in Brain Endothelial-Like Cells. Thyroid 2022; 32:860-870. [PMID: 35357974 DOI: 10.1089/thy.2021.0643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Background: Monocarboxylate transporter 8 (MCT8) deficiency is a rare genetic disease leading to a severe developmental delay due to a lack of thyroid hormones (THs) during critical stages of human brain development. Some MCT8-deficient patients are not as severely affected as others. Previously, we hypothesized that these patients' mutations do not affect the functionality but destabilize the MCT8 protein, leading to a diminished number of functional MCT8 molecules at the cell surface. Methods: We have already demonstrated that the chemical chaperone sodium phenylbutyrate (NaPB) rescues the function of these mutants by stabilizing their protein expression in an overexpressing cell system. Here, we expanded our previous work and used iPSC (induced pluripotent stem cell)-derived brain microvascular endothelial-like cells (iBMECs) as a physiologically relevant cell model of human origin to test for NaPB responsiveness. The effects on mutant MCT8 expression and function were tested by Western blotting and radioactive uptake assays. Results: We found that NaPB rescues decreased mutant MCT8 expression and restores transport function in iBMECs carrying patient's mutation MCT8-P321L. Further, we identified MCT10 as an alternative TH transporter in iBMECs that contributes to triiodothyronine uptake, the biological active TH. Our results indicate an upregulation of MCT10 after NaPB treatment. In addition, we detected an increase in thyroxine (T4) uptake after NaPB treatment that was not mediated by rescued MCT8 but an unidentified T4 transporter. Conclusions: We demonstrate that NaPB is suitable to stabilize a pathogenic missense mutation in a human-derived cell model. Further, it activates TH transport independent of MCT8. Both options fuel future studies to investigate repurposing the Food and Drug Administration-approved drug NaPB in selected cases of MCT8 deficiency.
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Affiliation(s)
- Doreen Braun
- Institut für Biochemie und Molekularbiologie, Medizinische Fakultät, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Simon Bohleber
- Institut für Biochemie und Molekularbiologie, Medizinische Fakultät, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Gad D Vatine
- The Department of Physiology and Cell Biology, Faculty of Health Sciences, The Regenerative Medicine and Stem Cell (RMSC) Research Center and the Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer Sheva, Israel
- Department of Biomedical Sciences, The Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Clive N Svendsen
- Department of Biomedical Sciences, The Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Ulrich Schweizer
- Institut für Biochemie und Molekularbiologie, Medizinische Fakultät, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
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3
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van Geest FS, Meima ME, Stuurman KE, Wolf NI, van der Knaap MS, Lorea CF, Poswar FO, Vairo F, Brunetti-Pierri N, Cappuccio G, Bakhtiani P, de Munnik SA, Peeters RP, Visser WE, Groeneweg S. Clinical and Functional Consequences of C-Terminal Variants in MCT8: A Case Series. J Clin Endocrinol Metab 2021; 106:539-553. [PMID: 33141165 PMCID: PMC7823235 DOI: 10.1210/clinem/dgaa795] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Indexed: 12/17/2022]
Abstract
CONTEXT Genetic variants in SLC16A2, encoding the thyroid hormone transporter MCT8, can cause intellectual and motor disability and abnormal serum thyroid function tests, known as MCT8 deficiency. The C-terminal domain of MCT8 is poorly conserved, which complicates prediction of the deleteriousness of variants in this region. We studied the functional consequences of 5 novel variants within this domain and their relation to the clinical phenotypes. METHODS We enrolled male subjects with intellectual disability in whom genetic variants were identified in exon 6 of SLC16A2. The impact of identified variants was evaluated in transiently transfected cell lines and patient-derived fibroblasts. RESULTS Seven individuals from 5 families harbored potentially deleterious variants affecting the C-terminal domain of MCT8. Two boys with clinical features considered atypical for MCT8 deficiency had a missense variant [c.1724A>G;p.(His575Arg) or c.1796A>G;p.(Asn599Ser)] that did not affect MCT8 function in transfected cells or patient-derived fibroblasts, challenging a causal relationship. Two brothers with classical MCT8 deficiency had a truncating c.1695delT;p.(Val566*) variant that completely inactivated MCT8 in vitro. The 3 other boys had relatively less-severe clinical features and harbored frameshift variants that elongate the MCT8 protein [c.1805delT;p.(Leu602HisfsTer680) and c.del1826-1835;p.(Pro609GlnfsTer676)] and retained ~50% residual activity. Additional truncating variants within transmembrane domain 12 were fully inactivating, whereas those within the intracellular C-terminal tail were tolerated. CONCLUSIONS Variants affecting the intracellular C-terminal tail of MCT8 are likely benign unless they cause frameshifts that elongate the MCT8 protein. These findings provide clinical guidance in the assessment of the pathogenicity of variants within the C-terminal domain of MCT8.
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Affiliation(s)
- Ferdy S van Geest
- Academic Center For Thyroid Disease, Department of Internal Medicine, Erasmus Medical Center, GD Rotterdam, The Netherlands
| | - Marcel E Meima
- Academic Center For Thyroid Disease, Department of Internal Medicine, Erasmus Medical Center, GD Rotterdam, The Netherlands
| | - Kyra E Stuurman
- Department of Clinical Genetics, Erasmus Medical Center, GD Rotterdam, The Netherlands
| | - Nicole I Wolf
- Department of Pediatric Neurology, Emma Children’s Hospital, Amsterdam University Medical Centre, AZ Amsterdam, Netherlands
- Amsterdam Neuroscience, HV Amsterdam, Netherlands
| | - Marjo S van der Knaap
- Department of Pediatric Neurology, Emma Children’s Hospital, Amsterdam University Medical Centre, AZ Amsterdam, Netherlands
- Amsterdam Neuroscience, HV Amsterdam, Netherlands
| | - Cláudia F Lorea
- Teaching Hospital of Universidade Federal de Pelotas, Brazil
| | - Fabiano O Poswar
- Medical Genetics Service, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
| | - Filippo Vairo
- Department of Clinical Genomics, Mayo Clinic, Rochester, Minnesota, USA
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota, USA
| | - Nicola Brunetti-Pierri
- Department of Translational Medicine, Federico II University, Naples, Italy
- Telethon Institute of Genetics and Medicine, Pozzuoli, Naples, Italy
| | - Gerarda Cappuccio
- Department of Translational Medicine, Federico II University, Naples, Italy
- Telethon Institute of Genetics and Medicine, Pozzuoli, Naples, Italy
| | | | - Sonja A de Munnik
- Department of Human Genetics, Radboud University Medical Centre Nijmegen, GA Nijmegen, the Netherlands
| | - Robin P Peeters
- Academic Center For Thyroid Disease, Department of Internal Medicine, Erasmus Medical Center, GD Rotterdam, The Netherlands
| | - W Edward Visser
- Academic Center For Thyroid Disease, Department of Internal Medicine, Erasmus Medical Center, GD Rotterdam, The Netherlands
| | - Stefan Groeneweg
- Academic Center For Thyroid Disease, Department of Internal Medicine, Erasmus Medical Center, GD Rotterdam, The Netherlands
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van Geest FS, Gunhanlar N, Groeneweg S, Visser WE. Monocarboxylate Transporter 8 Deficiency: From Pathophysiological Understanding to Therapy Development. Front Endocrinol (Lausanne) 2021; 12:723750. [PMID: 34539576 PMCID: PMC8440930 DOI: 10.3389/fendo.2021.723750] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 08/13/2021] [Indexed: 01/18/2023] Open
Abstract
Genetic defects in the thyroid hormone transporter monocarboxylate transporter 8 (MCT8) result in MCT8 deficiency. This disorder is characterized by a combination of severe intellectual and motor disability, caused by decreased cerebral thyroid hormone signalling, and a chronic thyrotoxic state in peripheral tissues, caused by exposure to elevated serum T3 concentrations. In particular, MCT8 plays a crucial role in the transport of thyroid hormone across the blood-brain-barrier. The life expectancy of patients with MCT8 deficiency is strongly impaired. Absence of head control and being underweight at a young age, which are considered proxies of the severity of the neurocognitive and peripheral phenotype, respectively, are associated with higher mortality rate. The thyroid hormone analogue triiodothyroacetic acid is able to effectively and safely ameliorate the peripheral thyrotoxicosis; its effect on the neurocognitive phenotype is currently under investigation. Other possible therapies are at a pre-clinical stage. This review provides an overview of the current understanding of the physiological role of MCT8 and the pathophysiology, key clinical characteristics and developing treatment options for MCT8 deficiency.
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5
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Gunay A, Shin HH, Gozutok O, Gautam M, Ozdinler PH. Importance of lipids for upper motor neuron health and disease. Semin Cell Dev Biol 2020; 112:92-104. [PMID: 33323321 DOI: 10.1016/j.semcdb.2020.11.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 10/12/2020] [Accepted: 11/11/2020] [Indexed: 12/18/2022]
Abstract
Building evidence reveals the importance of maintaining lipid homeostasis for the health and function of neurons, and upper motor neurons (UMNs) are no exception. UMNs are critically important for the initiation and modulation of voluntary movement as they are responsible for conveying cerebral cortex' input to spinal cord targets. To maintain their unique cytoarchitecture with a prominent apical dendrite and a very long axon, UMNs require a stable cell membrane, a lipid bilayer. Lipids can act as building blocks for many biomolecules, and they also contribute to the production of energy. Therefore, UMNs require sustained control over the production, utilization and homeostasis of lipids. Perturbations of lipid homeostasis lead to UMN vulnerability and progressive degeneration in diseases such as hereditary spastic paraplegia (HSP) and primary lateral sclerosis (PLS). Here, we discuss the importance of lipids, especially for UMNs.
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Affiliation(s)
- Aksu Gunay
- Department of Neurology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA, 60611
| | - Heather H Shin
- Department of Neurology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA, 60611
| | - Oge Gozutok
- Department of Neurology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA, 60611
| | - Mukesh Gautam
- Department of Neurology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA, 60611
| | - P Hande Ozdinler
- Department of Neurology, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA, 60611.
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6
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Braun D, Schweizer U. The Protein Translocation Defect of MCT8 L291R Is Rescued by Sodium Phenylbutyrate. Eur Thyroid J 2020; 9:269-280. [PMID: 33088796 PMCID: PMC7548921 DOI: 10.1159/000507439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 03/24/2020] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION The monocarboxylate transporter 8 (MCT8; SLC16A2) is a specific transporter for thyroid hormones. MCT8 deficiency, formerly known as the Allan-Herndon-Dudley syndrome, is a rare genetic disease that leads to neurological impairments and muscle weakness. Current experimental treatment options rely on thyromimetic agonists that do not depend on MCT8 for cellular uptake. Another approach comes from studies with the chemical chaperone sodium phenylbutyrate (NaPB), which was able to stabilize MCT8 mutants having protein folding defects in vitro. In addition, NaPB is known as a compound that assists with plasma membrane translocation. OBJECTIVE The pathogenic MCT8L291R leads to the same severe neurological impairments found for other MCT8-deficient patients but, unexpectedly, lacks alterations in plasma 3,3',5-triiodothyronine (T3) levels. Here we tried to unravel the underlying mechanism of MCT8 deficiency and tested whether the pathogenic MCT8L291R mutant responds to NaPB treatment. Therefore, we overexpressed the mutant in Madin-Darby canine kidney cells in the human choriocarcinoma cell line JEG1 and in COS7 cells of African green monkey origin. RESULTS In our recent study we describe that the MCT8L291R mutation most likely leads to a translocation defect. The pathogenic mutant is not located at the plasma membrane, but shows overlapping expression with a marker protein of the lysosome. Mutation of the corresponding amino acid in murine Mct8 (Mct8L223R) displays a similar effect on cell surface expression and transport function as seen before for MCT8L291R. NaPB was able to correct the translocation defect of MCT8L291R/Mct8L223R and restored protein function by increasing T3 transport activity. Furthermore, we detected enhanced mRNA levels of wild-type and mutant MCT8/Mct8 after NaPB treatment. The increase in mRNA levels could be an explanation for the positive effect on protein expression and function detected for wild-type MCT8. CONCLUSION NaPB is not only suitable for the treatment of mutations leading to misfolding and protein degradation, but also for a mutant wrongly sorted inside a cell which is otherwise functional.
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Affiliation(s)
- Doreen Braun
- *Doreen Braun, Institut für Biochemie und Molekularbiologie, Medizinische Fakultät, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 11, DE–53115 Bonn (Germany),
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Groeneweg S, van Geest FS, Peeters RP, Heuer H, Visser WE. Thyroid Hormone Transporters. Endocr Rev 2020; 41:5637505. [PMID: 31754699 DOI: 10.1210/endrev/bnz008] [Citation(s) in RCA: 98] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 11/07/2019] [Indexed: 02/08/2023]
Abstract
Thyroid hormone transporters at the plasma membrane govern intracellular bioavailability of thyroid hormone. Monocarboxylate transporter (MCT) 8 and MCT10, organic anion transporting polypeptide (OATP) 1C1, and SLC17A4 are currently known as transporters displaying the highest specificity toward thyroid hormones. Structure-function studies using homology modeling and mutational screens have led to better understanding of the molecular basis of thyroid hormone transport. Mutations in MCT8 and in OATP1C1 have been associated with clinical disorders. Different animal models have provided insight into the functional role of thyroid hormone transporters, in particular MCT8. Different treatment strategies for MCT8 deficiency have been explored, of which thyroid hormone analogue therapy is currently applied in patients. Future studies may reveal the identity of as-yet-undiscovered thyroid hormone transporters. Complementary studies employing animal and human models will provide further insight into the role of transporters in health and disease. (Endocrine Reviews 41: 1 - 55, 2020).
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Affiliation(s)
- Stefan Groeneweg
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Ferdy S van Geest
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Robin P Peeters
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Heike Heuer
- Department of Endocrinology, Diabetes and Metabolism, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - W Edward Visser
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
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8
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Remerand G, Boespflug-Tanguy O, Tonduti D, Touraine R, Rodriguez D, Curie A, Perreton N, Des Portes V, Sarret C. Expanding the phenotypic spectrum of Allan-Herndon-Dudley syndrome in patients with SLC16A2 mutations. Dev Med Child Neurol 2019; 61:1439-1447. [PMID: 31410843 DOI: 10.1111/dmcn.14332] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/07/2019] [Indexed: 01/01/2023]
Abstract
The aim of the study was to redefine the phenotype of Allan-Herndon-Dudley syndrome (AHDS), which is caused by mutations in the SLC16A2 gene that encodes the brain transporter of thyroid hormones. Clinical phenotypes, brain imaging, thyroid hormone profiles, and genetic data were compared to the existing literature. Twenty-four males aged 11 months to 29 years had a mutation in SLC16A2, including 12 novel mutations and five previously described mutations. Sixteen patients presented with profound developmental delay, three had severe intellectual disability with poor language and walking with an aid, four had moderate intellectual disability with language and walking abilities, and one had mild intellectual disability with hypotonia. Overall, eight had learned to walk, all had hypotonia, 17 had spasticity, 18 had dystonia, 12 had choreoathetosis, 19 had hypomyelination, and 10 had brain atrophy. Kyphoscoliosis (n=12), seizures (n=7), and pneumopathies (n=5) were the most severe complications. This study extends the phenotypic spectrum of AHDS to a mild intellectual disability with hypotonia. Developmental delay, hypotonia, hypomyelination, and thyroid hormone profile help to diagnose patients. Clinical course depends on initial severity, with stable acquisition after infancy; this may be adversely affected by neuro-orthopaedic, pulmonary, and epileptic complications. WHAT THIS PAPER ADDS: Mild intellectual disability is associated with SLC16A2 mutations. A thyroid hormone profile with a free T3 /T4 ratio higher than 0.75 can help diagnose patients. Patients with SLC16A2 mutations present a broad spectrum of neurological phenotypes that are also observed in other hypomyelinating disorders. Axial hypotonia is a consistent feature of Allan-Herndon-Dudley syndrome and leads to specific complications.
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Affiliation(s)
- Ganaelle Remerand
- Centre de Compétence des Leucodystrophies et Leucoencéphalopathies de Cause Rare, Pôle Femme et Enfant, Hôpital Estaing, Centre Hospitalier Universitaire de Clermont-Ferrand, Clermont-Ferrand, France
| | - Odile Boespflug-Tanguy
- Centre de Référence des Leucodystrophies et Leucoencéphalopathies de Cause Rare, Service de Neurologie Pédiatrique, Hôpital Robert Debré, Assistance Publique-Hôpitaux de Paris, Paris, France.,NeuroDiderot, INSERM UMR1141, Université Paris Diderot, Paris, France
| | - Davide Tonduti
- Unit of Child Neurology, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.,Unit of Child Neurology, V. Buzzi Children's Hospital, Milan, Italy
| | - Renaud Touraine
- Service de Génétique, Centre Hospitalier Universitaire de Saint-Etienne, Saint-Etienne, France
| | - Diana Rodriguez
- Sorbonne Université, GRC no. 19, Pathologies Congénitales du Cervelet-LeucoDystrophies, Assistance Publique-Hôpitaux de Paris, Hôpital Armand Trousseau, Paris, France.,Centre de Référence Neurogénétique, Service de Neurologie Pédiatrique, Assistance Publique-Hôpitaux de Paris, Hôpital Armand Trousseau, Paris, France
| | - Aurore Curie
- Centre de Référence des Déficiences Intellectuelles de Cause Rare, Service de Neurologie Pédiatrique, Centre Hospitalier Universitaire de Lyon, Hôpital Femme-Mère-Enfant, Lyon, France
| | - Nathalie Perreton
- CIC 1407Inserm, Centre Hospitalo-Universitaire de Lyon, Lyon, France
| | - Vincent Des Portes
- Centre de Référence des Déficiences Intellectuelles de Cause Rare, Service de Neurologie Pédiatrique, Centre Hospitalier Universitaire de Lyon, Hôpital Femme-Mère-Enfant, Lyon, France
| | - Catherine Sarret
- Centre de Compétence des Leucodystrophies et Leucoencéphalopathies de Cause Rare, Pôle Femme et Enfant, Hôpital Estaing, Centre Hospitalier Universitaire de Clermont-Ferrand, Clermont-Ferrand, France.,IGCNC, Université Clermont Auvergne, CNRS, SIGMA Clermont, Institut Pascal, Clermont-Ferrand, France
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9
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Masnada S, Groenweg S, Saletti V, Chiapparini L, Castellotti B, Salsano E, Visser WE, Tonduti D. Novel mutations in SLC16A2 associated with a less severe phenotype of MCT8 deficiency. Metab Brain Dis 2019; 34:1565-1575. [PMID: 31332729 DOI: 10.1007/s11011-019-00464-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Accepted: 07/08/2019] [Indexed: 02/08/2023]
Abstract
Mutations in the thyroid hormone transporter MCT8 cause severe intellectual and motor disability and abnormal serum thyroid function tests, a syndrome known as MCT8 deficiency (or: Allan-Herndon-Dudley syndrome, AHDS). Although the majority of patients are unable to sit or walk independently and do not develop any speech, some are able to walk and talk in simple sentences. Here, we report on two cases with such a less severe clinical phenotype and consequent gross delay in diagnosis. Genetic analyses revealed two novel hemizygous mutations in the SLC16A2 gene resulting in a p.Thr239Pro and a p.Leu543Pro substitution in the MCT8 protein. In vitro studies in transiently transfected COS-1 and JEG-3 cells, and ex vivo studies in patient-derived fibroblasts revealed substantial residual uptake capacity of both mutant proteins (Leu543Pro > Thr239Pro), providing an explanation for the less severe clinical phenotype. Both mutations impair MCT8 protein stability and interfere with proper subcellular trafficking. In one of the patients calcifications were observed in the basal ganglia at the age of 29 years; an abnormal neuroradiological feature at this age that has been linked to untreated (congenital) hypothyroidism and neural cretinism. Our studies extend on previous work by identifying two novel pathogenic mutations in SLC16A2 gene resulting in a mild clinical phenotype.
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Affiliation(s)
- Silvia Masnada
- Pediatric Neurology Unit, V. Buzzi Children's Hospital, Via Castelvetro 32, 20154, Milan, Italy
- Department of Brain and Behavioural Sciences, University of Pavia, Pavia, Italy
| | - Stefan Groenweg
- Department of Internal Medicine, Academic Center for Thyroid Diseases, Erasmus MC, University Medical Center, CN, Rotterdam, The Netherlands
| | - Veronica Saletti
- Child Neurology Department, IRCCS Foundation C. Besta Neurological Institute, Milan, Italy
| | - Luisa Chiapparini
- Neuroradiology Unit, IRCCS Foundation C. Besta Neurological Institute, Milan, Italy
| | - Barbara Castellotti
- Unit of Genetics of Neurodegenerative and Metabolic Diseases, IRCCS Foundation C. Besta Neurological Institute, Milan, Italy
| | - Ettore Salsano
- Unit of Neurodegenerative and Neurometabolic Rare Diseases, IRCCS Foundation C. Besta Neurological Institute, Milan, Italy
| | - W Edward Visser
- Department of Internal Medicine, Academic Center for Thyroid Diseases, Erasmus MC, University Medical Center, CN, Rotterdam, The Netherlands
| | - Davide Tonduti
- Pediatric Neurology Unit, V. Buzzi Children's Hospital, Via Castelvetro 32, 20154, Milan, Italy.
- Child Neurology Department, IRCCS Foundation C. Besta Neurological Institute, Milan, Italy.
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Groeneweg S, Kersseboom S, van den Berge A, Dolcetta-Capuzzo A, van Geest FS, van Heerebeek REA, Arjona FJ, Meima ME, Peeters RP, Visser WE, Visser TJ. In Vitro Characterization of Human, Mouse, and Zebrafish MCT8 Orthologues. Thyroid 2019; 29:1499-1510. [PMID: 31436139 DOI: 10.1089/thy.2019.0009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Background: Mutations in the thyroid hormone (TH) transporter monocarboxylate transporter 8 (MCT8) cause MCT8 deficiency, characterized by severe intellectual and motor disability and abnormal serum thyroid function tests. Various Mct8 knock-out mouse models as well as mct8 knock-out and knockdown zebrafish models are used as a disease model for MCT8 deficiency. Although important for model eligibility, little is known about the functional characteristics of the MCT8 orthologues in these species. Therefore, we here compared the functional characteristics of mouse (mm) MCT8 and zebrafish (dr) Mct8 to human (hs) MCT8. Methods: We performed extensive transport studies in COS-1 and JEG-3 cells transiently transfected with hsMCT8, drMct8, and mmMCT8. Protein expression levels and subcellular localization were assessed by immunoblotting, surface biotinylation, and immunocytochemistry. Sequence alignment and structural modeling were used to interpret functional differences between the orthologues. Results: hsMCT8, drMct8, and mmMCT8 all facilitated the uptake and efflux of 3,3'-diiodothyronine (3,3'-T2), rT3, triiodothyronine (T3), and thyroxine (T4), although the initial uptake rates of drMct8 were 1.5-4.0-fold higher than for hsMCT8 and mmMCT8. drMct8 exhibited 3-50-fold lower apparent IC50 values than hsMCT8 and mmMCT8 for all tested substrates, and substrate preference of drMct8 (3,3'-T2, T3 > T4 > rT3) differed from hsMCT8 and mmMCT8 (T3 > T4 > rT3, 3,3'-T2). Compared with hsMCT8 and mmMCT8, cis-inhibition studies showed that T3 uptake by drMct8 was inhibited at a lower concentration and by a broader spectrum of TH metabolites. Total and cell surface expression levels of drMct8 and hsMCT8 were equal and both significantly exceeded those of mmMCT8. Structural modeling located most non-conserved residues outside the substrate pore, except for H192 in hsMCT8, which is replaced by a glutamine in drMct8. However, a H192Q substituent of hsMCT8 did not alter its transporter characteristics. Conclusion: Our studies substantiate the eligibility of mice and zebrafish models for human MCT8 deficiency. However, differences in the intrinsic transporter properties of MCT8 orthologues may exist, which should be realized when comparing MCT8 deficiency in different in vivo models. Moreover, our findings may indicate that the protein domains outside the substrate channel may play a role in substrate selection and protein stability.
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Affiliation(s)
- Stefan Groeneweg
- Department of Internal Medicine, Erasmus Medical Center, Academic Center for Thyroid Diseases, Rotterdam, The Netherlands
| | - Simone Kersseboom
- Department of Internal Medicine, Erasmus Medical Center, Academic Center for Thyroid Diseases, Rotterdam, The Netherlands
| | - Amanda van den Berge
- Department of Internal Medicine, Erasmus Medical Center, Academic Center for Thyroid Diseases, Rotterdam, The Netherlands
| | - Anna Dolcetta-Capuzzo
- Department of Internal Medicine, Erasmus Medical Center, Academic Center for Thyroid Diseases, Rotterdam, The Netherlands
- Department of Endocrinology and Internal Medicine, San Raffaele Scientific Institute, Milan, Italy
| | - Ferdy S van Geest
- Department of Internal Medicine, Erasmus Medical Center, Academic Center for Thyroid Diseases, Rotterdam, The Netherlands
| | - Ramona E A van Heerebeek
- Department of Internal Medicine, Erasmus Medical Center, Academic Center for Thyroid Diseases, Rotterdam, The Netherlands
| | - Francisco J Arjona
- Department of Animal Ecology and Physiology, Institute for Water and Wetland Research, Faculty of Science, Radboud University Nijmegen, Nijmegen, The Netherlands
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Marcel E Meima
- Department of Internal Medicine, Erasmus Medical Center, Academic Center for Thyroid Diseases, Rotterdam, The Netherlands
| | - Robin P Peeters
- Department of Internal Medicine, Erasmus Medical Center, Academic Center for Thyroid Diseases, Rotterdam, The Netherlands
| | - W Edward Visser
- Department of Internal Medicine, Erasmus Medical Center, Academic Center for Thyroid Diseases, Rotterdam, The Netherlands
| | - Theo J Visser
- Department of Internal Medicine, Erasmus Medical Center, Academic Center for Thyroid Diseases, Rotterdam, The Netherlands
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11
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Braun D, Reuter U, Schweizer U. Modeling the Biochemical Phenotype of MCT8 Mutations In Vitro: Resolving a Troubling Inconsistency. Endocrinology 2019; 160:1536-1546. [PMID: 31127274 DOI: 10.1210/en.2019-00069] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 04/19/2019] [Indexed: 02/07/2023]
Abstract
Allan-Herndon-Dudley syndrome (AHDS) is a severe genetic disease caused by mutations in the monocarboxylate transporter 8 (MCT8) gene. MCT8 mediates transport of thyroid hormones in and out of cells, which is thought to play a pivotal role for embryonic and postnatal development of the human brain. Disconcertingly, MCT8R271H leads to a severe form of AHDS but shows residual transport activity when expressed in several types of cultured cells. Here we try to determine the mechanism behind the transport function of MCT8R271H found in overexpressing cell systems. Mutations of Arg271 were introduced into human MCT8 and stably transfected into Madin-Darby canine kidney cells and the human-derived cell line JEG1. Radioactive thyroid hormone-uptake experiments were performed to analyze the pH-dependent effect of the mutation on transport activity. Arg271His transports thyroid hormones in and out of cells in a pH-dependent manner. Its transport activity increases below pH 7.3 and is clearly diminished at physiological pH. The Michaelis constant of the mutant is unaltered, whereas the maximum velocity is reduced. The expression of Arg271His in JEG1 cells leads to an almost nonfunctional transporter at physiological pH replicating the human phenotype for this mutant in vitro and demonstrates, again, that mutant MCT8 activity depends on cellular background. The protonation of His271 at acidic pH restores activity of the mutant protein, which is not active in its deprotonated form at physiological pH. Thus, experimental parameters must be controlled carefully when modeling MCT8 deficiency in cells.
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Affiliation(s)
- Doreen Braun
- Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
| | - Uschi Reuter
- Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
| | - Ulrich Schweizer
- Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
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12
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Islam MS, Namba N, Ohata Y, Fujiwara M, Nakano C, Takeyari S, Miyata K, Nakano Y, Yamamoto K, Nakayama H, Kitaoka T, Kubota T, Ozono K. Functional analysis of monocarboxylate transporter 8 mutations in Japanese Allan-Herndon-Dudley syndrome patients. Endocr J 2019; 66:19-29. [PMID: 30369548 DOI: 10.1507/endocrj.ej18-0251] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Monocarboxylate transporter 8 (MCT8) facilitates T3 uptake into cells. Mutations in MCT8 lead to Allan-Herndon-Dudley syndrome (AHDS), which is characterized by severe psychomotor retardation and abnormal thyroid hormone profile. Nine uncharacterized MCT8 mutations in Japanese patients with severe neurocognitive impairment and elevated serum T3 levels were studied regarding the transport of T3. Human MCT8 (hMCT8) function was studied in wild-type (WT) or mutant hMCT8-transfected human placental choriocarcinoma cells (JEG3) by visualizing the locations of the proteins in the cells, detecting specific proteins, and measuring T3 uptake. We identified 6 missense (p.Arg445Ser, p.Asp498Asn, p.Gly276Arg, p.Gly196Glu, p.Gly401Arg, and p.Gly312Arg), 2 frameshift (p.Arg355Profs*64 and p.Tyr550Serfs*17), and 1 deletion (p.Pro561del) mutation(s) in the hMCT8 gene. All patients exhibited clinical characteristics of AHDS with high free T3, low-normal free T4, and normal-elevated TSH levels. All tested mutants were expressed at the protein level, except p.Arg355Profs*64 and p.Tyr550Serfs*17, which were truncated, and were inactive in T3 uptake, excluding p.Arg445Ser and p.Pro561del mutants, compared with WT-hMCT8. Immunocytochemistry revealed plasma membrane localization of p.Arg445Ser and p.Pro561del mutants similar with WT-hMCT8. The other mutants failed to localize in significant amount(s) in the plasma membrane and instead localized in the cytoplasm. These data indicate that p.Arg445Ser and p.Pro561del mutants preserve residual function, whereas p.Asp498Asn, p.Gly276Arg, p.Gly196Glu, p.Gly401Arg, p.Gly312Arg, p.Arg355Profs*64, and p.Tyr550Serfs*17 mutants lack function. These findings suggest that the mutations in MCT8 cause loss of function by reducing protein expression, impairing trafficking of protein to plasma membrane, and disrupting substrate channel.
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Affiliation(s)
- Mohammad Saiful Islam
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Noriyuki Namba
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
- Department of Pediatrics, Osaka Hospital, Japan Community Healthcare Organization, Osaka, Japan
| | - Yasuhisa Ohata
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
- The First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, Suita, Japan
| | - Makoto Fujiwara
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
- Center for Clinical and Translational Research, Maine Medical Center Research Institute, Scarborough, Maine, USA
| | - Chiho Nakano
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
- The First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, Suita, Japan
| | - Shinji Takeyari
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Kei Miyata
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Yukako Nakano
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Kenichi Yamamoto
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
- Department of Statistical Genetics, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Hirofumi Nakayama
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
- The Japan Environment and Children's Study, Osaka Unit Center, Suita, Japan
| | - Taichi Kitaoka
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Takuo Kubota
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Keiichi Ozono
- Department of Pediatrics, Graduate School of Medicine, Osaka University, Suita, Japan
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13
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Sweeney MD, Zhao Z, Montagne A, Nelson AR, Zlokovic BV. Blood-Brain Barrier: From Physiology to Disease and Back. Physiol Rev 2019; 99:21-78. [PMID: 30280653 PMCID: PMC6335099 DOI: 10.1152/physrev.00050.2017] [Citation(s) in RCA: 1157] [Impact Index Per Article: 231.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 04/17/2018] [Accepted: 04/17/2018] [Indexed: 12/12/2022] Open
Abstract
The blood-brain barrier (BBB) prevents neurotoxic plasma components, blood cells, and pathogens from entering the brain. At the same time, the BBB regulates transport of molecules into and out of the central nervous system (CNS), which maintains tightly controlled chemical composition of the neuronal milieu that is required for proper neuronal functioning. In this review, we first examine molecular and cellular mechanisms underlying the establishment of the BBB. Then, we focus on BBB transport physiology, endothelial and pericyte transporters, and perivascular and paravascular transport. Next, we discuss rare human monogenic neurological disorders with the primary genetic defect in BBB-associated cells demonstrating the link between BBB breakdown and neurodegeneration. Then, we review the effects of genes underlying inheritance and/or increased susceptibility for Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease, and amyotrophic lateral sclerosis (ALS) on BBB in relation to other pathologies and neurological deficits. We next examine how BBB dysfunction relates to neurological deficits and other pathologies in the majority of sporadic AD, PD, and ALS cases, multiple sclerosis, other neurodegenerative disorders, and acute CNS disorders such as stroke, traumatic brain injury, spinal cord injury, and epilepsy. Lastly, we discuss BBB-based therapeutic opportunities. We conclude with lessons learned and future directions, with emphasis on technological advances to investigate the BBB functions in the living human brain, and at the molecular and cellular level, and address key unanswered questions.
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Affiliation(s)
- Melanie D Sweeney
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California ; and Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California , Los Angeles, California
| | - Zhen Zhao
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California ; and Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California , Los Angeles, California
| | - Axel Montagne
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California ; and Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California , Los Angeles, California
| | - Amy R Nelson
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California ; and Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California , Los Angeles, California
| | - Berislav V Zlokovic
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California , Los Angeles, California ; and Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California , Los Angeles, California
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14
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Groeneweg S, van den Berge A, Meima ME, Peeters RP, Visser TJ, Visser WE. Effects of Chemical Chaperones on Thyroid Hormone Transport by MCT8 Mutants in Patient-Derived Fibroblasts. Endocrinology 2018; 159:1290-1302. [PMID: 29309566 DOI: 10.1210/en.2017-00846] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 12/29/2017] [Indexed: 12/26/2022]
Abstract
Mutations in the thyroid hormone (TH) transporter monocarboxylate transporter 8 (MCT8) result in severe intellectual and motor disability. At present, no effective therapy is available to restore TH signaling in MCT8-dependent tissues. Recent in vitro studies in stable overexpression cell models suggested that the function of certain mutant MCT8 proteins, specifically those that affect protein stability and intracellular trafficking (e.g., p.F501del), could be partially recovered by chemical chaperones. However, the effects of chaperones have not been demonstrated in other commonly used models for MCT8 deficiency, including transient overexpression models and patient-derived fibroblasts. Here, we demonstrate that the chemical chaperone 4-phenylbutyric acid (PBA) similarly potentiates the T3 transport function of wild-type and p.F501del mutant MCT8 in transiently transfected COS-1 cells by increasing MCT8 messenger RNA, total protein, and cell surface expression levels. Although PBA also increased the cell surface expression levels of the p.R445L mutant, no functional improvement was observed, which is in line with the proposed important role of Arg445 in substrate translocation. In contrast, PBA showed only minimal effects in ex vivo studies using control or p.F501del patient-derived fibroblasts. Moreover, the MCT8-specific inhibitor silychristin did not change these minimal effects, suggesting that the underlying mechanism is unrelated to the rescue of functional MCT8. Together, these findings indicate that the potency of chaperones to rescue mutant MCT8 function strongly depends on the cellular model and stress the need for further preclinical studies before clinically available chaperones should be considered as a treatment option in patients with MCT8 deficiency.
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Affiliation(s)
- Stefan Groeneweg
- The Rotterdam Thyroid Center and Department of Internal Medicine, Erasmus Medical Center, Rotterdam, Netherlands
| | - Amanda van den Berge
- The Rotterdam Thyroid Center and Department of Internal Medicine, Erasmus Medical Center, Rotterdam, Netherlands
| | - Marcel E Meima
- The Rotterdam Thyroid Center and Department of Internal Medicine, Erasmus Medical Center, Rotterdam, Netherlands
| | - Robin P Peeters
- The Rotterdam Thyroid Center and Department of Internal Medicine, Erasmus Medical Center, Rotterdam, Netherlands
| | - Theo J Visser
- The Rotterdam Thyroid Center and Department of Internal Medicine, Erasmus Medical Center, Rotterdam, Netherlands
| | - W Edward Visser
- The Rotterdam Thyroid Center and Department of Internal Medicine, Erasmus Medical Center, Rotterdam, Netherlands
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15
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16
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Abstract
Transport of thyroid hormone (TH) across the plasma membrane is essential for intracellular TH metabolism and action, and this is mediated by specific transporter proteins. During the last two decades several transporters capable of transporting TH have been identified, including monocarboxylate transporter 8 (MCT8), MCT10 and organic anion transporting polypeptide 1C1 (OATP1C1). In particular MCT8 and OATP1C1 are important for the regulation of local TH activity in the brain and thus for brain development. MCT8 is a protein containing 12 transmembrane domains, and is encoded by the SLC16A2 gene located on the X chromosome. It facilitates both TH uptake and efflux across the cell membrane. Male subjects with hemizygous mutations in MCT8 are afflicted with severe intellectual and motor disability, also known as the Allan-Herndon-Dudley syndrome (AHDS), which goes together with low serum T4 and high T3 levels. This review concerns molecular and clinical aspects of MCT8 function.
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Affiliation(s)
- Stefan Groeneweg
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands.
| | - W Edward Visser
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands.
| | - Theo J Visser
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands.
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17
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van Mullem AA, van Gucht ALM, Visser WE, Meima ME, Peeters RP, Visser TJ. Effects of thyroid hormone transporters MCT8 and MCT10 on nuclear activity of T3. Mol Cell Endocrinol 2016; 437:252-260. [PMID: 27492966 DOI: 10.1016/j.mce.2016.07.037] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 07/10/2016] [Accepted: 07/27/2016] [Indexed: 11/22/2022]
Abstract
Transport of thyroid hormone (TH) across the plasma membrane is necessary for the genomic action of T3 mediated by its nuclear T3 receptor. MCT8 and MCT10 have been identified as important TH transporters. Mutations in MCT8 result in severe psychomotor retardation. In addition to TH transport into the cell, MCT8 and MCT10 also facilitate TH efflux from cells. Therefore, the aim of this study was to examine if MCT8 and MCT10 increase the availability of T3 for its nuclear receptor rather than generate a rapid equilibrium between cellular and serum T3. T3 action was investigated in JEG3 cells co-transfected with TRβ1 and a T3 response element-driven luciferase construct, and T3 metabolism was analyzed in cells transfected with type 3 deiodinase (D3). In addition, cells were transfected with MCT8 or MCT10 and/or the cytoplasmic T3-binding protein mu-crystallin (CRYM). Luciferase signal was markedly stimulated by incubating cells for 24 h with 1 nM T3, but this response was not augmented by MCT8 or MCT10 expression. Limiting the time of T3 exposure to 1-6 h and co-transfection with CRYM allowed for a modest increase in luciferase response to T3. In contrast, T3 metabolism by D3 was potently stimulated by MCT8 or MCT10 expression, but it was not affected by expression of CRYM. These results suggest that MCT8 and MCT10 by virtue of their bidirectional T3 transport have less effect on steady-state nuclear T3 levels than on T3 levels at the cell periphery where D3 is located. CRYM alters the dynamics of cellular TH transport but its exact function in the cellular distribution of TH remains to be determined.
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Affiliation(s)
- Alies A van Mullem
- Department of Internal Medicine and Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Anja L M van Gucht
- Department of Internal Medicine and Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - W Edward Visser
- Department of Internal Medicine and Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Marcel E Meima
- Department of Internal Medicine and Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Robin P Peeters
- Department of Internal Medicine and Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Theo J Visser
- Department of Internal Medicine and Rotterdam Thyroid Center, Erasmus University Medical Center, Rotterdam, The Netherlands.
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18
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Zwanziger D, Schmidt M, Fischer J, Kleinau G, Braun D, Schweizer U, Moeller LC, Biebermann H, Fuehrer D. The long N-terminus of the human monocarboxylate transporter 8 is a target of ubiquitin-dependent proteasomal degradation which regulates protein expression and oligomerization capacity. Mol Cell Endocrinol 2016; 434:278-87. [PMID: 27222294 DOI: 10.1016/j.mce.2016.05.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 04/19/2016] [Accepted: 05/20/2016] [Indexed: 11/24/2022]
Abstract
Monocarboxylate transporter 8 (MCT8) equilibrates thyroid hormones between the extra- and the intracellular sides. MCT8 exists either with a short or a long N-terminus, but potential functional differences between both variants are yet not known. We, therefore, generated MCT8 constructs which are different in N-terminal length: MCT8(1-613), MCT8(25-613), MCT8(49-613) and MCT8(75-613). The M75G substitution prevents translation of MCT8(75-613) and ensures expression of full-length MCT8 protein. The K56G substitution was made to prevent ubiquitinylation. Cell-surface expression, localization and proteasomal degradation were investigated using C-terminally GFP-tagged MCT8 constructs (HEK293 and MDCK1 cells) and oligomerization capacity was determined using N-terminally HA- and C-terminally FLAG-tagged MCT8 constructs (COS7 cells). MCT8(1-613)-GFP showed a lower protein expression than the shorter MCT8(75-613)-GFP protein. The proteasome inhibitor lactacystin increased MCT8(1-613)-GFP protein amount, suggesting proteasomal degradation of MCT8 with the long N-terminus. Ubiquitin conjugation of MCT8(1-613)-GFP was found by immuno-precipitation. A diminished ubiquitin conjugation caused by K56G substitution resulted in increased MCT8(1-613)-GFP protein expression. Sandwich ELISA was performed to investigate if the bands at higher molecular weight observed in Western blot analysis are due to MCT8 oligomerization, which was indeed shown. Our data imply a role of the long N-terminus of MCT8 as target of ubiquitin-dependent proteasomal degradation affecting MCT8 amount and subsequently oligomerization capacity.
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Affiliation(s)
- Denise Zwanziger
- University of Duisburg-Essen, Department of Endocrinology and Metabolism and Division of Laboratory Research, Hufelandstraße 55, 45147 Essen, Germany.
| | - Mathias Schmidt
- University of Duisburg-Essen, Department of Endocrinology and Metabolism and Division of Laboratory Research, Hufelandstraße 55, 45147 Essen, Germany.
| | - Jana Fischer
- Charitè-Berlin, Institute of Experimental Pediatric Endocrinology, Augustenburgerplatz 1, 13353 Berlin, Germany.
| | - Gunnar Kleinau
- Charitè-Berlin, Institute of Experimental Pediatric Endocrinology, Augustenburgerplatz 1, 13353 Berlin, Germany.
| | - Doreen Braun
- Rheinische Friedrich-Wilhelms Universität Bonn, Institut für Biochemie und Molekularbiologie, Nussallee 11, 53115 Bonn, Germany.
| | - Ulrich Schweizer
- Rheinische Friedrich-Wilhelms Universität Bonn, Institut für Biochemie und Molekularbiologie, Nussallee 11, 53115 Bonn, Germany.
| | - Lars Christian Moeller
- University of Duisburg-Essen, Department of Endocrinology and Metabolism and Division of Laboratory Research, Hufelandstraße 55, 45147 Essen, Germany.
| | - Heike Biebermann
- Charitè-Berlin, Institute of Experimental Pediatric Endocrinology, Augustenburgerplatz 1, 13353 Berlin, Germany.
| | - Dagmar Fuehrer
- University of Duisburg-Essen, Department of Endocrinology and Metabolism and Division of Laboratory Research, Hufelandstraße 55, 45147 Essen, Germany.
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19
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Johannes J, Braun D, Kinne A, Rathmann D, Köhrle J, Schweizer U. Few Amino Acid Exchanges Expand the Substrate Spectrum of Monocarboxylate Transporter 10. Mol Endocrinol 2016; 30:796-808. [PMID: 27244477 PMCID: PMC5426580 DOI: 10.1210/me.2016-1037] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 05/24/2016] [Indexed: 02/07/2023] Open
Abstract
Monocarboxylate transporters (MCTs) belong to the SLC16 family within the major facilitator superfamily of transmembrane transporters. MCT8 is a thyroid hormone transporter mutated in the Allan-Herndon-Dudley syndrome, a severe psychomotor retardation syndrome. MCT10 is closely related to MCT8 and is known as T-type amino acid transporter. Both transporters mediate T3 transport, but although MCT8 also transports rT3 and T4, these compounds are not efficiently transported by MCT10, which, in contrast, transports aromatic amino acids. Based on the 58% amino acid identity within the transmembrane regions among MCT8 and MCT10, we reasoned that substrate specificity may be primarily determined by a small number of amino acid differences between MCT8 and MCT10 along the substrate translocation channel. Inspecting the homology model of MCT8 and a structure-guided alignment between both proteins, we selected 8 amino acid positions and prepared chimeric MCT10 proteins with selected amino acids changed to the corresponding amino acids in MCT8. The MCT10 mutant harboring 8 amino acid substitutions was stably expressed in Madin-Darby canine kidney 1 cells and found to exhibit T4 transport activity. We then successively reduced the number of amino acid substitutions and eventually identified a minimal set of 2-3 amino acid exchanges which were sufficient to allow T4 transport. The resulting MCT10 chimeras exhibited KM values for T4 similar to MCT8 but transported T4 at a slower rate. The acquisition of T4 transport by MCT10 was associated with complete loss of the capacity to transport Phe, when Tyr184 was mutated to Phe.
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Affiliation(s)
- Jörg Johannes
- Institut für Biochemie und Molekularbiologie (J.J., D.B., U.S.), Rheinische Friedrich-Wilhelms-Universität, 53115 Bonn, Germany; and Institut für Experimentelle Endokrinologie (J.J., A.K., D.R., J.K.), Charité-Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Doreen Braun
- Institut für Biochemie und Molekularbiologie (J.J., D.B., U.S.), Rheinische Friedrich-Wilhelms-Universität, 53115 Bonn, Germany; and Institut für Experimentelle Endokrinologie (J.J., A.K., D.R., J.K.), Charité-Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Anita Kinne
- Institut für Biochemie und Molekularbiologie (J.J., D.B., U.S.), Rheinische Friedrich-Wilhelms-Universität, 53115 Bonn, Germany; and Institut für Experimentelle Endokrinologie (J.J., A.K., D.R., J.K.), Charité-Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Daniel Rathmann
- Institut für Biochemie und Molekularbiologie (J.J., D.B., U.S.), Rheinische Friedrich-Wilhelms-Universität, 53115 Bonn, Germany; and Institut für Experimentelle Endokrinologie (J.J., A.K., D.R., J.K.), Charité-Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Josef Köhrle
- Institut für Biochemie und Molekularbiologie (J.J., D.B., U.S.), Rheinische Friedrich-Wilhelms-Universität, 53115 Bonn, Germany; and Institut für Experimentelle Endokrinologie (J.J., A.K., D.R., J.K.), Charité-Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Ulrich Schweizer
- Institut für Biochemie und Molekularbiologie (J.J., D.B., U.S.), Rheinische Friedrich-Wilhelms-Universität, 53115 Bonn, Germany; and Institut für Experimentelle Endokrinologie (J.J., A.K., D.R., J.K.), Charité-Universitätsmedizin Berlin, 13353 Berlin, Germany
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20
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Charzewska A, Wierzba J, Iżycka-Świeszewska E, Bekiesińska-Figatowska M, Jurek M, Gintowt A, Kłosowska A, Bal J, Hoffman-Zacharska D. Hypomyelinating leukodystrophies - a molecular insight into the white matter pathology. Clin Genet 2016; 90:293-304. [DOI: 10.1111/cge.12811] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 05/24/2016] [Accepted: 05/25/2016] [Indexed: 12/23/2022]
Affiliation(s)
- A. Charzewska
- Institute of Mother and Child, Department of Medical Genetics; Warsaw Poland
| | - J. Wierzba
- Medical University of Gdańsk; Department of Paediatrics, Haemathology & Oncology, Department of General Nursery; Gdańsk Poland
| | - E. Iżycka-Świeszewska
- Medical University of Gdańsk; Department of Pathology & Neuropathology; Copernicus Hospital, Department of Patomorphology; Gdańsk Poland
| | | | - M. Jurek
- Institute of Mother and Child, Department of Medical Genetics; Warsaw Poland
| | - A. Gintowt
- Medical University of Gdańsk; Department of Biology and Genetics; Gdańsk Poland
| | - A. Kłosowska
- Medical University of Gdańsk; Department of Paediatrics, Haemathology & Oncology, Department of General Nursery; Gdańsk Poland
| | - J. Bal
- Institute of Mother and Child, Department of Medical Genetics; Warsaw Poland
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21
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Bourgeois NMA, Van Herck SLJ, Vancamp P, Delbaere J, Zevenbergen C, Kersseboom S, Darras VM, Visser TJ. Characterization of Chicken Thyroid Hormone Transporters. Endocrinology 2016; 157:2560-74. [PMID: 27070099 DOI: 10.1210/en.2015-2025] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Thyroid hormone (TH) transmembrane transporters are key regulators of TH availability in target cells where correct TH signaling is essential for normal development. Although the chicken embryo is a valuable model for developmental studies, the only functionally characterized chicken TH transporter so far is the organic anion transporting polypeptide 1C1 (OATP1C1). We therefore cloned the chicken L-type amino acid transporter 1 (LAT1) and the monocarboxylate transporters 8 (MCT8) and 10 (MCT10), and functionally characterized them, together with OATP1C1, in JEG3, COS1, and DF-1 cells. In addition, we used in situ hybridization to study their mRNA expression pattern during development. MCT8 and OATP1C1 are both high affinity transporters for the prohormone T4, whereas receptor-active T3 is preferably transported by MCT8 and MCT10. The latter one shows lower affinity but has a high Vmax and seems to be especially good at T3 export. Also, LAT1 has a lower affinity for its preferred substrate 3,3'-diiodothyronine. Reverse T3 is transported by all 4 TH transporters and is a good export product for OATP1C1. TH transporters are strongly expressed in eye (LAT1, MCT8, MCT10), pancreas (LAT1, MCT10), kidney, and testis (MCT8). Their extensive expression in the central nervous system, especially at the brain barriers, indicates an important role in brain development. In conclusion, we show TH transport by chicken MCT8, MCT10, and LAT1. Together with OATP1C1, these transporters have functional characteristics similar to their mammalian orthologs and are interesting target genes to further elucidate the role of THs during embryonic development.
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Affiliation(s)
- Nele M A Bourgeois
- Laboratory of Comparative Endocrinology (N.M.A.B., S.L.J.V.H., P.V., J.D., V.M.D.), Department of Biology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; and Department of Internal Medicine (C.Z., S.K., T.J.V.), Erasmus University Medical Center, 3015 GE Rotterdam, The Netherlands
| | - Stijn L J Van Herck
- Laboratory of Comparative Endocrinology (N.M.A.B., S.L.J.V.H., P.V., J.D., V.M.D.), Department of Biology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; and Department of Internal Medicine (C.Z., S.K., T.J.V.), Erasmus University Medical Center, 3015 GE Rotterdam, The Netherlands
| | - Pieter Vancamp
- Laboratory of Comparative Endocrinology (N.M.A.B., S.L.J.V.H., P.V., J.D., V.M.D.), Department of Biology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; and Department of Internal Medicine (C.Z., S.K., T.J.V.), Erasmus University Medical Center, 3015 GE Rotterdam, The Netherlands
| | - Joke Delbaere
- Laboratory of Comparative Endocrinology (N.M.A.B., S.L.J.V.H., P.V., J.D., V.M.D.), Department of Biology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; and Department of Internal Medicine (C.Z., S.K., T.J.V.), Erasmus University Medical Center, 3015 GE Rotterdam, The Netherlands
| | - Chantal Zevenbergen
- Laboratory of Comparative Endocrinology (N.M.A.B., S.L.J.V.H., P.V., J.D., V.M.D.), Department of Biology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; and Department of Internal Medicine (C.Z., S.K., T.J.V.), Erasmus University Medical Center, 3015 GE Rotterdam, The Netherlands
| | - Simone Kersseboom
- Laboratory of Comparative Endocrinology (N.M.A.B., S.L.J.V.H., P.V., J.D., V.M.D.), Department of Biology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; and Department of Internal Medicine (C.Z., S.K., T.J.V.), Erasmus University Medical Center, 3015 GE Rotterdam, The Netherlands
| | - Veerle M Darras
- Laboratory of Comparative Endocrinology (N.M.A.B., S.L.J.V.H., P.V., J.D., V.M.D.), Department of Biology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; and Department of Internal Medicine (C.Z., S.K., T.J.V.), Erasmus University Medical Center, 3015 GE Rotterdam, The Netherlands
| | - Theo J Visser
- Laboratory of Comparative Endocrinology (N.M.A.B., S.L.J.V.H., P.V., J.D., V.M.D.), Department of Biology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; and Department of Internal Medicine (C.Z., S.K., T.J.V.), Erasmus University Medical Center, 3015 GE Rotterdam, The Netherlands
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22
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Ono E, Ariga M, Oshima S, Hayakawa M, Imai M, Ochiai Y, Mochizuki H, Namba N, Ozono K, Miyata I. Three novel mutations of the MCT8 (SLC16A2) gene: individual and temporal variations of endocrinological and radiological features. Clin Pediatr Endocrinol 2016; 25:23-35. [PMID: 27212794 PMCID: PMC4860513 DOI: 10.1297/cpe.25.23] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 12/17/2015] [Indexed: 11/13/2022] Open
Abstract
We performed genetic analysis and clinical investigations for three patients with
suspected monocarboxylate transporter 8 (MCT8) deficiency. On genetic analysis of the
MCT8(SLC16A2) gene, novel mutations (c.1333C>A;
p.R445S, c.587G>A; p.G196E and c.1063_1064insCTACC; p.R355PfsX64) were identified in
each of three patients. Although thyroid function tests (TFTs) showed the typical pattern
of MCT8 deficiency at the time of genetic diagnosis in all patients, two patients
occasionally were euthyroid. A TRH test revealed low response, exaggerated response and
normal response of TSH, respectively. Endocrinological studies showed gonadotropin (Gn)
deficiency in two adult patients. On ultrasonography, goiter was detected in one patient.
Interestingly, pituitary magnetic resonance imaging (MRI) demonstrated atrophy and
thinness of the pituitary gland in two patients. Our findings suggest that thyroid status
in patients with MCT8 deficiency varies with time of examination, and repeated TFTs are
necessary for patients suspected of MCT8 deficiency before genetic analysis. In addition,
it is noteworthy that some variations were observed on the TRH test and ultrasonography of
the thyroid gland in the present study. Morphological abnormality of the pituitary gland
may be found in some patients, while Gn deficiency should be considered as one of the
complications.
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Affiliation(s)
- Erina Ono
- Department of Pediatrics, The Jikei University School of Medicine, Tokyo, Japan; Department of Pediatrics, Tokyo Metropolitan Kita Medical and Rehabilitation Center for the Disabled, Tokyo, Japan
| | - Masamichi Ariga
- Department of Pediatrics, Tokyo Metropolitan Kita Medical and Rehabilitation Center for the Disabled, Tokyo, Japan
| | - Sakiko Oshima
- Department of Pediatrics, Tokyo Metropolitan Kita Medical and Rehabilitation Center for the Disabled, Tokyo, Japan
| | - Mika Hayakawa
- Department of Pediatrics, Tokyo Metropolitan Kita Medical and Rehabilitation Center for the Disabled, Tokyo, Japan
| | - Masayuki Imai
- Department of Pediatrics, Tokyo Metropolitan Kita Medical and Rehabilitation Center for the Disabled, Tokyo, Japan
| | - Yukikatsu Ochiai
- Department of Pediatrics, Tokyo Metropolitan Kita Medical and Rehabilitation Center for the Disabled, Tokyo, Japan
| | - Hiroshi Mochizuki
- Department of Endocrinology and Metabolism, Saitama Children's Medical Center, Saitama, Japan
| | - Noriyuki Namba
- Department of Pediatrics, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Keiichi Ozono
- Department of Pediatrics, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Ichiro Miyata
- Department of Pediatrics, The Jikei University School of Medicine, Tokyo, Japan
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23
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Thevenon J, Duffourd Y, Masurel-Paulet A, Lefebvre M, Feillet F, El Chehadeh-Djebbar S, St-Onge J, Steinmetz A, Huet F, Chouchane M, Darmency-Stamboul V, Callier P, Thauvin-Robinet C, Faivre L, Rivière JB. Diagnostic odyssey in severe neurodevelopmental disorders: toward clinical whole-exome sequencing as a first-line diagnostic test. Clin Genet 2016; 89:700-7. [PMID: 26757139 DOI: 10.1111/cge.12732] [Citation(s) in RCA: 176] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 01/05/2016] [Accepted: 01/07/2016] [Indexed: 01/03/2023]
Abstract
The current standard of care for diagnosis of severe intellectual disability (ID) and epileptic encephalopathy (EE) results in a diagnostic yield of ∼50%. Affected individuals nonetheless undergo multiple clinical evaluations and low-yield laboratory tests often referred to as a 'diagnostic odyssey'. This study was aimed at assessing the utility of clinical whole-exome sequencing (WES) in individuals with undiagnosed and severe forms of ID and EE, and the feasibility of its implementation in routine practice by a small regional genetic center. We performed WES in a cohort of 43 unrelated individuals with undiagnosed ID and/or EE. All individuals had undergone multiple clinical evaluations and diagnostic tests over the years, with no definitive diagnosis. Sequencing data analysis and interpretation were carried out at the local molecular genetics laboratory. The diagnostic rate of WES reached 32.5% (14 out of 43 individuals). Genetic diagnosis had a direct impact on clinical management in four families, including a prenatal diagnostic test in one family. Our data emphasize the clinical utility and feasibility of WES in individuals with undiagnosed forms of ID and EE and highlight the necessity of close collaborations between ordering physicians, molecular geneticists, bioinformaticians and researchers for accurate data interpretation.
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Affiliation(s)
- J Thevenon
- Fédération Hospitalo-Universitaire Médecine Translationnelle et Anomalies du Développement (TRANSLAD), Centre Hospitalier Universitaire Dijon, Dijon, France.,Centre de Génétique et Centre de Référence Anomalies du Développement et Syndromes Malformatifs de l'Interrégion Est, Centre Hospitalier Universitaire Dijon, Dijon, France.,Equipe d'Accueil 4271, Génétique des Anomalies du Développement, Université de Bourgogne, Dijon, France
| | - Y Duffourd
- Fédération Hospitalo-Universitaire Médecine Translationnelle et Anomalies du Développement (TRANSLAD), Centre Hospitalier Universitaire Dijon, Dijon, France.,Equipe d'Accueil 4271, Génétique des Anomalies du Développement, Université de Bourgogne, Dijon, France
| | - A Masurel-Paulet
- Fédération Hospitalo-Universitaire Médecine Translationnelle et Anomalies du Développement (TRANSLAD), Centre Hospitalier Universitaire Dijon, Dijon, France.,Centre de Génétique et Centre de Référence Anomalies du Développement et Syndromes Malformatifs de l'Interrégion Est, Centre Hospitalier Universitaire Dijon, Dijon, France
| | - M Lefebvre
- Fédération Hospitalo-Universitaire Médecine Translationnelle et Anomalies du Développement (TRANSLAD), Centre Hospitalier Universitaire Dijon, Dijon, France.,Centre de Génétique et Centre de Référence Anomalies du Développement et Syndromes Malformatifs de l'Interrégion Est, Centre Hospitalier Universitaire Dijon, Dijon, France
| | - F Feillet
- Service de Médecine Infantile 1, Centre de Référence des Maladies Héréditaires du Métabolisme, Centre Hospitalier Universitaire Brabois-Enfants, Vandœuvre-lès-Nancy, France
| | | | - J St-Onge
- Fédération Hospitalo-Universitaire Médecine Translationnelle et Anomalies du Développement (TRANSLAD), Centre Hospitalier Universitaire Dijon, Dijon, France.,Equipe d'Accueil 4271, Génétique des Anomalies du Développement, Université de Bourgogne, Dijon, France
| | - A Steinmetz
- Fédération Hospitalo-Universitaire Médecine Translationnelle et Anomalies du Développement (TRANSLAD), Centre Hospitalier Universitaire Dijon, Dijon, France.,Centre de Génétique et Centre de Référence Anomalies du Développement et Syndromes Malformatifs de l'Interrégion Est, Centre Hospitalier Universitaire Dijon, Dijon, France
| | - F Huet
- Service de Pédiatrie 1, Centre Hospitalier Universitaire Dijon, Dijon, France
| | - M Chouchane
- Service de Pédiatrie 1, Centre Hospitalier Universitaire Dijon, Dijon, France
| | - V Darmency-Stamboul
- Service de Pédiatrie 1, Centre Hospitalier Universitaire Dijon, Dijon, France
| | - P Callier
- Fédération Hospitalo-Universitaire Médecine Translationnelle et Anomalies du Développement (TRANSLAD), Centre Hospitalier Universitaire Dijon, Dijon, France.,Equipe d'Accueil 4271, Génétique des Anomalies du Développement, Université de Bourgogne, Dijon, France.,Laboratoire de Génétique Chromosomique et Moléculaire, Plateau Technique de Biologie, Centre Hospitalier Universitaire Dijon, Dijon, France
| | - C Thauvin-Robinet
- Fédération Hospitalo-Universitaire Médecine Translationnelle et Anomalies du Développement (TRANSLAD), Centre Hospitalier Universitaire Dijon, Dijon, France.,Centre de Génétique et Centre de Référence Anomalies du Développement et Syndromes Malformatifs de l'Interrégion Est, Centre Hospitalier Universitaire Dijon, Dijon, France.,Equipe d'Accueil 4271, Génétique des Anomalies du Développement, Université de Bourgogne, Dijon, France
| | - L Faivre
- Fédération Hospitalo-Universitaire Médecine Translationnelle et Anomalies du Développement (TRANSLAD), Centre Hospitalier Universitaire Dijon, Dijon, France.,Centre de Génétique et Centre de Référence Anomalies du Développement et Syndromes Malformatifs de l'Interrégion Est, Centre Hospitalier Universitaire Dijon, Dijon, France.,Equipe d'Accueil 4271, Génétique des Anomalies du Développement, Université de Bourgogne, Dijon, France
| | - J B Rivière
- Fédération Hospitalo-Universitaire Médecine Translationnelle et Anomalies du Développement (TRANSLAD), Centre Hospitalier Universitaire Dijon, Dijon, France.,Equipe d'Accueil 4271, Génétique des Anomalies du Développement, Université de Bourgogne, Dijon, France.,Laboratoire de Génétique Chromosomique et Moléculaire, Plateau Technique de Biologie, Centre Hospitalier Universitaire Dijon, Dijon, France
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24
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Zhao Z, Nelson AR, Betsholtz C, Zlokovic BV. Establishment and Dysfunction of the Blood-Brain Barrier. Cell 2016; 163:1064-1078. [PMID: 26590417 DOI: 10.1016/j.cell.2015.10.067] [Citation(s) in RCA: 1027] [Impact Index Per Article: 128.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Indexed: 12/11/2022]
Abstract
Structural and functional brain connectivity, synaptic activity, and information processing require highly coordinated signal transduction between different cell types within the neurovascular unit and intact blood-brain barrier (BBB) functions. Here, we examine the mechanisms regulating the formation and maintenance of the BBB and functions of BBB-associated cell types. Furthermore, we discuss the growing evidence associating BBB breakdown with the pathogenesis of inherited monogenic neurological disorders and complex multifactorial diseases, including Alzheimer's disease.
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Affiliation(s)
- Zhen Zhao
- Department of Physiology and Biophysics and the Zilkha Neurogenetic Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA 90089, USA
| | - Amy R Nelson
- Department of Physiology and Biophysics and the Zilkha Neurogenetic Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA 90089, USA
| | - Christer Betsholtz
- Department of Immunology, Genetics, and Pathology, Rudbeck Laboratory, 75185 Uppsala, Sweden
| | - Berislav V Zlokovic
- Department of Physiology and Biophysics and the Zilkha Neurogenetic Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA 90089, USA.
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25
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Fischer J, Kleinau G, Müller A, Kühnen P, Zwanziger D, Kinne A, Rehders M, Moeller LC, Führer D, Grüters A, Krude H, Brix K, Biebermann H. Modulation of monocarboxylate transporter 8 oligomerization by specific pathogenic mutations. J Mol Endocrinol 2015; 54:39-50. [PMID: 25527620 DOI: 10.1530/jme-14-0272] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The monocarboxylate transporter 8 (MCT8) is a member of the major facilitator superfamily (MFS). These membrane-spanning proteins facilitate translocation of a variety of substrates, MCT8 specifically transports iodothyronines. Mutations in MCT8 are the underlying cause of severe X-linked psychomotor retardation. At the molecular level, such mutations led to deficiencies in substrate translocation due to reduced cell-surface expression, impaired substrate binding, or decreased substrate translocation capabilities. However, the causal relationships between genotypes, molecular features of mutated MCT8, and patient characteristics have not yet been comprehensively deciphered. We investigated the relationship between pathogenic mutants of MCT8 and their capacity to form dimers (presumably oligomeric structures) as a potential regulatory parameter of the transport function of MCT8. Fourteen pathogenic variants of MCT8 were investigated in vitro with respect to their capacity to form oligomers. Particular mutations close to the substrate translocation channel (S194F, A224T, L434W, and R445C) were found to inhibit dimerization of MCT8. This finding is in contrast to those for other transporters or transmembrane proteins, in which substitutions predominantly at the outer-surface inhibit oligomerization. Moreover, specific mutations of MCT8 located in transmembrane helix 2 (del230F, V235M, and ins236V) increased the capacity of MCT8 variants to dimerize. We analyzed the localization of MCT8 dimers in a cellular context, demonstrating differences in MCT8 dimer formation and distribution. In summary, our results add a new link between the functions (substrate transport) and protein organization (dimerization) of MCT8, and might be of relevance for other members of the MFS. Finally, the findings are discussed in relationship to functional data combined with structural-mechanistical insights into MCT8.
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Affiliation(s)
- Jana Fischer
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Gunnar Kleinau
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Anne Müller
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Peter Kühnen
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Denise Zwanziger
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Anita Kinne
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Maren Rehders
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Lars C Moeller
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Dagmar Führer
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Annette Grüters
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Heiko Krude
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Klaudia Brix
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
| | - Heike Biebermann
- Institut für Experimentelle Pädiatrische EndokrinologieCharité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, GermanyLeibniz-Institut für Molekulare PharmakologieBerlin, GermanyUniversitätsklinikum EssenKlinik für Endokrinologie und Stoffwechselerkrankungen, Essen, GermanyJacobs University BremenBremen, Germany
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26
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Schweizer U, Johannes J, Bayer D, Braun D. Structure and function of thyroid hormone plasma membrane transporters. Eur Thyroid J 2014; 3:143-53. [PMID: 25538896 PMCID: PMC4224232 DOI: 10.1159/000367858] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 08/26/2014] [Indexed: 01/25/2023] Open
Abstract
Thyroid hormones (TH) cross the plasma membrane with the help of transporter proteins. As charged amino acid derivatives, TH cannot simply diffuse across a lipid bilayer membrane, despite their notorious hydrophobicity. The identification of monocarboxylate transporter 8 (MCT8, SLC16A2) as a specific and very active TH transporter paved the way to the finding that mutations in the MCT8 gene cause a syndrome of psychomotor retardation in humans. The purpose of this review is to introduce the current model of transmembrane transport and highlight the diversity of TH transmembrane transporters. The interactions of TH with plasma transfer proteins, T3 receptors, and deiodinase are summarized. It is shown that proteins may bind TH owing to their hydrophobic character in hydrophobic cavities and/or by specific polar interaction with the phenolic hydroxyl, the aminopropionic acid moiety, and by weak polar interactions with the iodine atoms. These findings are compared with our understanding of how TH transporters interact with substrate. The presumed effects of mutations in MCT8 on protein folding and transport function are explained in light of the available homology model.
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Affiliation(s)
- Ulrich Schweizer
- Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
- *Prof. Dr. Ulrich Schweizer, Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 11, DE-53115 Bonn (Germany), E-Mail
| | - Jörg Johannes
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Dorothea Bayer
- Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Doreen Braun
- Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
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X-exome sequencing in Finnish families with intellectual disability--four novel mutations and two novel syndromic phenotypes. Orphanet J Rare Dis 2014; 9:49. [PMID: 24721225 PMCID: PMC4022384 DOI: 10.1186/1750-1172-9-49] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 03/31/2014] [Indexed: 01/18/2023] Open
Abstract
Background X-linked intellectual disability (XLID) is a group of genetically heterogeneous disorders characterized by substantial impairment in cognitive abilities, social and behavioral adaptive skills. Next generation sequencing technologies have become a powerful approach for identifying molecular gene mutations relevant for diagnosis. Methods & objectives Enrichment of X-chromosome specific exons and massively parallel sequencing was performed for identifying the causative mutations in 14 Finnish families, each of them having several males affected with intellectual disability of unknown cause. Results We found four novel mutations in known XLID genes. Two mutations; one previously reported missense mutation (c.1111C > T), and one novel frameshift mutation (c. 990_991insGCTGC) were identified in SLC16A2, a gene that has been linked to Allan-Herndon-Dudley syndrome (AHDS). One novel missense mutation (c.1888G > C) was found in GRIA3 and two novel splice donor site mutations (c.357 + 1G > C and c.985 + 1G > C) were identified in the DLG3 gene. One missense mutation (c.1321C > T) was identified in the candidate gene ZMYM3 in three affected males with a previously unrecognized syndrome characterized by unique facial features, aortic stenosis and hypospadia was detected. All of the identified mutations segregated in the corresponding families and were absent in > 100 Finnish controls and in the publicly available databases. In addition, a previously reported benign variant (c.877G > A) in SYP was identified in a large family with nine affected males in three generations, who have a syndromic phenotype. Conclusions All of the mutations found in this study are being reported for the first time in Finnish families with several affected male patients whose etiological diagnoses have remained unknown to us, in some families, for more than 30 years. This study illustrates the impact of X-exome sequencing to identify rare gene mutations and the challenges of interpreting the results. Further functional studies are required to confirm the cause of the syndromic phenotypes associated with ZMYM3 and SYP in this study.
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